Bài giảng Using Information Technology 11e - Chapter 5: Hardware: Input & Output

ChapterHardware: Input & Output5Chapter Topics2UNIT 5A: Input Hardware5.1 Keyboards 5.2 Pointing Devices5.3 Source Data-Entry Devices5.4 The Future of InputUNIT 5B: Output Hardware5.5 Softcopy Output: Display Screens5.6 Hardcopy Output: Printers5.7 Mixed Output: Sound, Voice, & Video5.8 The Future of Output5.9 Quality of Life: Health & ErgonomicsInput HardwareDevices that translate data into a form the computer can processTranslates words, numbers, sounds, and pictures into binary 0s and 1s (off or on electrical signals or light pulses)Output HardwareDevices that translate information processed by the computer into a form humans can understandTranslates binary code into words, numbers, sounds, and pictures3UNIT 5A: Input HardwareThe three major types of input hardware are keyboards, pointing devices, and source data-entry devices.455.1 Keyboards6Keyboards: convert letters, numbers, and characters into electrical signalsEnglish keyboards differ from foreign language keyboardsHow keyboards work:You press a keyThis interrupts the current flowing through the circuitsProcessor determines where the break occursIt compares the location of the break with the (x,y) character map for the language on the keyboard’s ROM chipA character is stored in keyboard memory7(continued)Keyboards (continued)The character is then sent to PC as a data stream via wire or wireless connectionOS interprets its own operating-system-specific commands and sends the others to the application for interpretationMost keyboards are QWERTY – named for the first six letters on the top left of the keyboard.Keyboards are either tactile (physical) or touch screen (virtual)8Keyboard types104 – 108 keys desktop standard80 – 85 keys for laptopsWiredConnect to CPU via a serial or USB portWireless use eitherIR (infrared) technologyRadio Frequency (RF) technology9Terminal Types Dumb Terminalsa.k.a. Video Display Terminal (VDT)Has display screen and keyboardCan do input and output only – no data processingIntelligent TerminalsHas screen, processor, keyboard, and memoryCan perform some independent functionsAutomated teller machine; point-of-sale terminal; mobile data terminal105.2 Pointing DevicePointing devices include the mouse and its variants, the touch screen, and various forms of pen input.Pointing devices control the position of the cursor or pointer on the screen and allow the user to select options displayed on the screen.Mouse is the principal pointing device.Mechanical mouse: a ball inside the mouse touches the desktop surface and rolls with the mouse.Optical mouse: uses laser beams and special chips to encode data for the computer.The mouse controls the mouse pointer on the screen – for example, an arrow, rectangle, pointing finger.When the mouse pointer changes to an I-beam, that indicates that text can be entered.The mouse has one to five buttons, used for various functions, such as clicking on and dragging items on the screen.12Pointing Devices (continued)TrackballA movable ball mounted on top of a stationary deviceGood for locations where a mouse can’t move around enoughTouchpadTo use: slide your finger over this small flat surface Click by tapping you finger on the surfaceMay require more practice to use than a mouseUsed on laptopsPointing stickLocated between the keys on a laptop keyboard, a pointing stick is a pressure-sensitive device that allows the user to control the pointer by directing the stick with one finger.13Pointing Devices (continued)Touch ScreensA video display screen sensitized to receive input from a finger touch.Used in ATMs, information, kiosks, reservation kiosks, voting machines, cellphones, tablets, and e-books.Multitouch ScreensDisplay screens that allow two or more fingers or other gestures such as pinching motions to be recognized as input at any one time. It allows pinching and stretching gestures on the screen to control zooming.Pen inputUses a pen-like stylus for input. Uses handwriting recognition to translate cursive writing into data (handwriting recognition).14Pointing Devices (continued)Light penA light-sensitive penlike device that uses a wired connection to a computer terminalBring the pen to the desired point on the display screen and press a button to identify the screen locationUsed by graphics artists, engineers, and in situations that require covered handsDigitizerUses an electronic pen or puck to convert drawings and photos to digital dataDigitizing tablets are often used in architecture15Pointing Devices (continued)Digital PenWriting instrumentWriters can write on paperA tiny camera in the pen tip captures the writingA microchip in the pen converts the pen to digital inkThe writing is sent as an image file to the computerSome versions require special paper165.3 Source Data-Entry DevicesScanning & Reading Devices—Source data-entry devices that create machine-readable data and feed it directly into the computer (no keyboard is used)ScannersUse light-sensing equipment to translate images of text, drawings, and photos into digital formImage scanners are used in electronic imagingResolution refers to the image sharpness, measured in dots per inch (dpi)Flatbed scanners work like photocopiers – the image is placed on the glass surface, then scannedOther types are sheet-fed, handheld, and drum18Bar-Code Readers (source data entry)Photoelectric (optical) scanners that translate bar code symbols into digital codeThe digital code is then sent to a computerThe computer looks up the item and displays its name and associated informationBar code types1D (regular vertical stripes) holds up to 16 ASCII characters2D (different-sized rectangles) can hold 1,000 to 2,000 ASCII characters3D is “bumpy” code that differentiates by symbol heightCan be used on metal, hard rubber, other tough surfaces19Radio-Frequency Identification (RFID)Based on an identifying tag bearing a microchip that contains specific code numbers. These code numbers are read by the radio waves of a scanner linked to a database. Active RFID tags have their own power source and can transmit signals over a distance to a reader device.Passive RFID tags have no battery power of their own and must be read by some sort of scanner.RFID tags of both types are used for a wide range of purposes and are starting to replace bar codes in many situations. Mark Recognition Readers (source data entry)MICR – magnetic-ink character recognitionUses special magnetized inksMust be read by a special scanner that reads this inkUsed on bank checksOMR – optical mark recognitionUses a special scanner that reads bubble (pencil) marksUsed in standardized tests such as the SAT and GREOCR – optical character recognitionConverts scanned text from images (pictures of the text) to an editable text format21Image-Capture DevicesDigital CamerasUse a light-sensitive processor chip to capture photographic images in digital form and store them on a small disk in the camera or on flash memory cards.Most can be connected to a PC by USB; smartphones include digital cameras.Webcams Video cameras attached to a computer to record live moving images then post them to a website in real time.Can be attached externally or built into the computer/device.Frame-grabber video cardCan capture and digitize 1 frame at a timeFull-motion video cardCan convert analog to digital signals at rates up to 30 frames per secondLooks like a motion picture2223Digital CameraAudio-Input DevicesRecord analog sound and translate it into digital files for storage and processingTwo ways to digitize audio (often via microphone)Sound BoardAn add-on board in a computer that converts analog sound to digital sound, stores it, and plays it back to speakers or ampMIDI BoardStands for Musical Instrument Digital ExchangeUses a standard for the interchange between musical instruments, synthesizers, and computers24Speech-Recognition SystemsUse a microphone or telephone as an input device. Converts a person’s speech into digital signals by comparing against 200,000 or so stored patterns.Used in places where people need their hands free – warehouses, car radios, stock exchange trades.Helpful for people with visual or physical disabilities that prevent them from using other input devices.25Speech RecognitionSensorsInput device that collects specific data directly from the environment and transmits it to a computer.Can be used to detect speed, movement, weight, pressure, temperature, humidity, wind, current, fog, gas, smoke, light, shapes, images, earthquakes, etc.27Biometric-Input DevicesBiometrics is the science of measuring individual body characteristics, then using them to identify a person through a fingerprint, hand, eye, voice, or facial characteristics.Example: notebook computers equipped with biometric sensors that read fingerprints, instead of passwords, before allowing access to networks.Airport and building security systems use biometrics.285.4 The Future of InputData will be input from more and more locations.Use of source data entry will increase.Better input devices for people with disabilitiesBetter speech recognitionBetter touch and gesture-recognition inputPattern recognition and improved biometricsBrainwave input devicesUNIT 5B: Output HardwareSoftcopy = data shown on a display screen or is in audio or voice form; it exists only electronically. This kind of output is not tangible; it cannot be touched. You can touch disks on which programs are stored, but the software itself is intangible. Hardcopy = tangible output, usually printed. The principal examples are printouts, whether text or graphics, from printers. Film, including microfilm and microfiche, is also considered hardcopy output.315.5 Softcopy OutputDisplay ScreensFeatures of display screens to consider include screen dimension, screen clarity, and color and resolution standards.Screen size & aspect ratioThe active display area is the size of a computer screen measured diagonally from corner to corner in inches. Desktop computers are commonly 15–30 inches (laptops 12–18 inches, tablets 8.4–14.1 inches, and smartphones 2.5–4.1 inches).The aspect ratio is the proportional relationship of a display screen’s width and height. Standard displays have a 4:3 aspect ratio (4 units wide to 3 units high); wide-screen displays have 16:9 or 16:10.Screen Clarity Dot pitch (dp) is the amount of space between adjacent pixels (square picture elements) on screen.The closer the pixels, the crisper the image.Get .25 dp or better.Resolution refers to the image sharpness.The more pixels, the better the resolution.Expressed in dots per inch (dpi) .35pixelScreen Clarity (continued) Color depth (bit depth) is the number of bits stored in a dot (pixel).The higher the number the more true the colors.24-bit color depth is better than 8-bit color depth, but it needs more video card memory.Refresh rate is the number of times per second the pixels are recharged – a higher rate gives less flicker.36Standard bit depthsfor color8-bit—256 colors16-bit—65,536 colors24-bit—16,777,216 colorsMicrocomputers come with graphics cards (video cards) that work with the screen.Graphics cards have their own memory (VRAM), which stores each pixel’s information.The more VRAM, the higher the resolution you can use.Desktop publishers, graphics artists, and gamers need lots of VRAM.37Types of Display DevicesThe most common type of display screens, flat-panel displays are made up of two plates of glass separated by a layer of a substance in which light is manipulated.One type of flat-panel display is the liquid crystal display (LCD), in which molecules of liquid crystal line up in a way that alters their optical properties, creating images on the screen by transmitting or blocking light.Other types of displays:Plasma displays: A layer of gas is sandwiched between two glass plates, and when voltage is applied, the gas releases ultraviolet light, which activates the pixels on the screen and forms an image. Although expensive, plasma monitors offer brighter colors and screen sizes up to 150 inches wide; however, they usually do not last as long as other display types.Cathode-ray tube (CRT) and others: Falling out of use.Multiple screens: Splitting the monitor display area into multiple screens, to view different documents at once.5.6 Hardcopy OutputPrintersPrinters print text and graphics on paper or other hardcopy materials.Printer resolution is measured by dpi (dots per inch); 1,200 x 1,200 is the most common for microcomputers.Printers are either impact or nonimpact – impact printers (dot-matrix printer) print by striking the paper directly; nonimpact printers (such as laser printers and inkjet printers) do not have direct contact with the hardcopy medium.41Like a dot-matrix printer, a laser printer creates images with dots. However, as in a photocopying machine, these images are produced on a drum, treated with an electrically charged inklike toner (powder), and then transferred from drum to paper. Laser printers run with software called a page description language (PDL) , which tells the printer how to lay out the printed page and supports various fonts. A laser printer comes with one or both types of PDL: PostScript or PCL (Printer Control Language. In desktop publishing, PostScript is the preferred PDL. Laser printers have their own CPU, ROM, and memory (RAM), usually 16 megabytes (expandable generally up to 512 megabytes for higher-cost printers). When you need to print out graphics-heavy color documents, your printer will need more memory.43Laser PrinterInkjet printers spray onto paper small, electrically charged droplets of ink from four or more nozzles through holes in a matrix at high speed. Like laser and dot-matrix printers, inkjet printers form images with little dots. Inkjet printers commonly have a dpi of 4,800 x 1,200; they spray ink onto the page a line at a time, in both high-quality black-and-white text and high-quality color graphics.45Inkjet PrinterNonimpact printers also include:Thermal printers: Low- to medium-resolution printers that use a type of coated paper that darkens when heat is applied to it; typically used in business for bar-code label applications and for printing cash register receipts.Thermal wax-transfer printers: Print a wax-based ink onto paper. After it becomes cool, the wax adheres permanently to the paper. Because of their waterfastness, these labels find uses in industrial label printing.Photo printers: Specialized machines for printing continuous-tone photo prints , with special paper and color dyes.46Multifunction printersPrinters that combine several capabilities:PrintingScanningCopyingFaxingCost less and take up less space than buying the four separate office machines.But if one component malfunctions, so will the other functions.47Plotters : Designed for large-format printingSpecialized output device designed to produce large high-quality, 3-D graphics in a variety of colors.Used by architects, engineers, and map-makers.Pen plotters use one or more colored pens.Electrostatic plotters lie partially flat on a table and use toner as photocopiers do.Large-format plotters are large-scale inkjet printers used by graphic artists.485.7 MIXED OUTPUT: SOUND, VOICE, & VIDEOMixed Output: Sound, Voice, & Video Sound output—produces digitized sounds, even “3-D” sound.You need a sound card and sound software.Good speakers can improve the sound.Voice output—converts digital data into speechlike sounds.Used in phone trees, cars, toys and games, GPS systems, and TTS (text-to-speech) systems for hearing-impaired people.Video output—photographic images played quickly enough to appear as full-motion.Requires powerful processor and video card.Video files are large, so a lot of storage is needed, too.Videoconferencing is a form of video output.505.8 The Future of Output51More unusual forms of outputMore data used in (Big Data)More realistic outputBetter and cheaper display screensPrinters that use less inkMovie-quality video for PCs Increased use of 3D output5.9 Quality of LifeHealth & ErgonomicsHealth MattersOveruse injuries and repetitive stress injuries:Result when muscle groups are forced through fast, repetitive motions.May effect data-entry operators who average 15,000 keystrokes an hour.May effect computer users whose monitor, keyboard, and workstation are not arranged for comfort.Carpal tunnel syndrome: Caused by pressure on the median nerve in the wrist, through short repetitive movements.Eyestrain, headaches, back and neck pains can be problems.Electromagnetic fields may be harmful.54Ergonomics is the methodology of designing a workplace to make working conditions and equipment safer and more efficient.Keyboards must be placed at the correct height depending on each worker’s size; detachable keyboards are useful.Monitor refresh rates must be fast enough to avoid eyestrain.Monitor heights must be correct for comfortable viewing; use a tilting screen.Wrist rests may help avoid carpal tunnel syndrome.55